The present invention relates to pressurized cylinders and, in particular, to protective caps for pressurized cylinders.
Cylinders containing pressurized fluids, such as oxygen and flammable gases for example, are provided at one end with a valved discharge opening. Protection of the valve is of major concern because a rupturing of the valve (resulting for example from a severe impact) may produce serious harm since the cylinders are highly pressurized (e.g., cylinders commonly in use are pressurized to 5,000 psi). For that reason, it has been necessary to provide a rugged protective cap which fits atop the cylinder in overlying relation to the valve. Virtually all such caps presently in use are formed of steel and are attached to the cylinder by means of a threaded coupling (e.g., female threads on the cap which screw onto male threads on the cylinder).
While such caps have been able to meet minimum safety standards, the threaded coupling presents certain drawbacks. For example, the threads tend to rust and corrode, especially when used in corrosive atmospheres (e.g., when used offshore), Also, in the event that a cylinder is subjected to a severe impact, the threads may become distorted. In such instances, removal of the cap may become very difficult, if not impossible to achieve. It is not uncommon under such circumstances for operators to harshly handle the cylinder (e.g., by striking the cap) in attempting to break loose the threads. Such abuse can lead to a rupturing of the valve. Furthermore, since the male threads are often carried on a ring or collar fastened to the cylinder (e.g., by peening) it is possible that attempts to free a rusted thread may cause the ring to become dislodged from the cylinder, whereupon the ring remains attached to the cylinder, but is free to rotate. In that event, removal of the cap becomes virtually impossible and the cylinder is rendered unusable.
Even in cases where rusted caps are eventually removed without a rupturing of the valve, the difficulty encountered usually produces substantial mounts of wasted time and effort on the part of handlers.
Efforts to design a threadless coupling have heretofore not meet with commercial success due, in large measure, to the inability of such couplings to meet the safety standards required of the caps. For example, the integrity of cap securement is tested by (1) dropping the capped end of the cylinder from ten feet onto cement in a vertical direction and also in a direction oriented at a 45 degree angle to vertical, and (2) toppling a standing cylinder such that the cap impacts against another cylinder lying on the ground whereby the cap of the falling cylinder takes the full impact in a direction generally perpendicular to the cylinder axis. Such impacts can be of considerable magnitude, since the cylinders can be quite heavy, e.g., on the order of 200 pounds for example.
It has heretofore been proposed in Wayer et al U.S. Pat. No. 1,948,953 issued Feb. 27, 1934 to shorten the time required to install and remove the cap by employing a coupling comprising lugs on the cylinders which, upon subsequent rotation of the cap, become wedged against corresponding lugs on the cap. Such an arrangement which constitues, in effect, a shortening of the extent of the standard threaded coupling between the cap and cylinder, presents certain shortcomings. For example, the wedging engagement between the lugs renders the lugs highly susceptible to being locked shut, e.g., by rust, dirt, deformation of the lugs. This possibility is apparently recognized by Wayer et al who provide a hole at the top of the cap for receiving a bar wrench to enable the cap to be rotated.
Also, in such an arrangement, the location of the cap lugs at the very bottom of the cap renders the cap more susceptible to stress failure because there is no material of the cap supporting the cap from below.
It is, therefore, an object of the present invention to minimize or obviate problems of the type discussed above.
Another object is to provide a threadless coupling for pressurized cylinder caps which is easily attachable and releasable.
A further object is to provide such a threadless coupling which satisfies the customary safety standards regarding pressurized cylinder caps.